After a startup or during a location update, a mobile terminal needs to perform a network search. A network search capability of the terminal may be considered as an important index for evaluating terminal quality. Taking a Wideband Code Division Multiple Access (Wideband Code Division Multiple Access, WCDMA) system as an example, a network search process of the terminal may be divided into two sub-processes, namely Public Land Mobile Network (Public Land Mobile Network, PLMN) selection and cell search.
A PLMN is jointly identified by a Mobile Country Code (Mobile Country Code, MCC, 3 numbers) and a Mobile Network Code (Mobile Network Code, MNC, 2 or 3 numbers). Each country has one or more PLMNs. Taking China as an example, a network code of a Global System for Mobile Communications (Global System for Mobile Communications, GSM) network of China Mobile Communications Corporation is represented by using “00”; and a network code of a GMS network of China Unicom Corporation is represented by using “01”. The PLMN is formed by multiple cells, and a cell is a minimum coverage unit in a mobile communication network.
Both the GSM and the WCDMA are divided into a Circuit Switching (Circuit Switching, CS) domain and a Packet Switching (Packet Switching, PS) domain. At present, most terminals support the CS and the PS at the same time, namely support a voice service and a GPRS data service at the same time. After the terminal is started or offline, the terminal performs the network search, first selects a PLMN and then searches for a cell that belongs to the PLMN. After finding the cell meeting conditions, the terminal obtains information of adjacent cells from a system broadcast message; according to the information, the terminal selects and stays resident in a cell with the best signal among these cells and performs location registration. A location registration process is initiated in both the CS domain and the PS domain. At present, both the GSM and the WCDMA require that the CS domain and PS domain of the terminal registration must belong to a same network.
When the terminal performs location registration or location update, after a location registration or location update request is initiated, if the CS domain rejects terminal access, the terminal performs network reselection. If the PS domain rejects the access, while the location registration or location update in the CS domain already succeeds, the terminal does not perform PLMN reselection, and stays resident in the network.
A basic principle of the foregoing existing network selection manner of the terminal is that, for the terminal supporting the CS and the PS at the same time, when the location registration or location update in the CS domain is rejected by the network, the terminal reselects a network; when the location registration or location update in the PS domain is rejected by the network, the terminal does not reselect a network, which cause a user to be incapable of performing a packet switching service, thus seriously affecting user experience as the packet switching service is being developed increasingly nowadays. For example, for a data card user, although a data card supports the CS and PS at the same time, the user hardly uses a voice CS service. Therefore, the data card user generally expects that the PS data service is ensured more reliably.